This invention relates to a one-chip semiconductor device comprising a semiconductor substrate and a data processing IC, e.g., a microcomputer and a microprocessor, formed on the substrate. More particularly, it relates to a one-chip semiconductor device in which a data processing can be performed without errors even if the power supply voltage changes.
Generally, a one-chip semiconductor device which can process data comprises a semiconductor substrate and a C-MOS semiconductor IC with a clock generating circuit and a data processing circuit. The substrate has power supply terminals, data terminals and other terminals. The power supply terminals are connected to an external power source, and the data terminals are coupled to an external device which the one-chip semiconductor device controls. The clock generating circuit generates clock signals as long as the power source applies voltage thereto. The clock signals are supplied to the data processing circuit and used as sync signals. The data processing circuit comprises a program memory (ROM), a data memory (RAM), an arithmetic logic unit (ALU) and an input-output section (I/O). It receives data from the outer device through the data terminals, processes the data, and outputs the same to the external device through the data terminals.
The semiconductor device has no means to prevent the data processing circuit from malfunctioning, even if the power supply voltage changes. A control signal must be supplied to the device to interrupt or initialize the data processing circuit. The device therefore has an external control terminal for supplying such a control signal. When a change of the voltage is detected, an interruption signal or a reset signal is generated outside the device. The signal is supplied to the data processing circuit through the external control terminal. As a result, the circuit stops processing data and saves it, or is initialized to start processing the same data again. Hence, the circuit makes no errors.
Therefore, the conventional device requires a control circuit for detecting changes of the power supply voltage and supplying an interruption signal or a reset signal to the data processing circuit. Any apparatus with the device must include the control circuit as well. Moreover, the one-chip semiconductor device needs to have a control terminal to receive the control signal. This inevitably increases the number of terminals the device requires. Further, the device must be able to interrupt the data processing circuit and is inevitably complex.